Immediate Goal: To generate TEL-AML1 transgenic zebrafish model and investigate the secondary genetic events that accentuate leukemia development. Career Development Goal: To develop an independent career in leukemia research. Research Project: The t(12;21) chromosomal translocation, which generates the TEL-AML1 fusion gene, is the most frequent structural genetic abnormality in childhood cancer, and is exclusively associated with precursor B-cell acute lymphoblastic leukemia (ALL). Evidence suggests that the TEL-AML1 translocation usually occurs In Utero during fetal hematopoiesis and constitutes an initiating or first-hit mutation that is necessary but insufficient for leukemia development. The aim of this proposal is to identify the secondary genetic events required for the development of TEL-AML1-induced leukemia. The two specific aims designed to test the central hypothesis that TEL-AML1 fusion protein requires secondary genetic events to induce leukemic transformation are: 1) To generate stable transgenic zebrafish lines expressing the TEL-AML1 fusion protein, and evaluate the effects of transgene expression on zebrafish hematopoiesis and leukemic development;2) To develop a "second-hit" model in TEL-AML1 transgenic zebrafish by investigating the altered expression of the normal zebrafish TEL and histone acetyltransferase activity, both implicated in TEL-AML1 leukemic development, and in parallel, by initiating a retroviral insertional mutagenesis screen in transgenic zebrafish aimed at identifying cancer genes that synergize with the TEL-AML1 fusion protein in ALL development. Resources available to carry out these aims include our established TEL-AML1 transgenic founders and their progeny, a zebrafish mutant for histone acetyltransferase, and a retrovirus expressing zebrafish-specific reporter gene. The zebrafish system is uniquely suitable for these experiments in that it presents a vertebrate model with a versatile biology, genetic flexibility, conserved hematopoietic development, and the opportunity to conduct transgenesis and subsequent mutagenesis. The ability to perform a large-scale phenotype-driven mutational screen to identify cooperating events that accelerate leukemic development in the presence of chromosomal fusion proteins represents the unique advantage of this model. The identification of crucial genes in the leukemic pathway in these studies may identify novel targets for leukemia specific therapies. Although this application is for a K22 career development award, without an institutional affiliation, I believe that having a postdoctoral fellowship at the National Cancer Institute for three years prepared me to develop an independent cancer research career, and that the favorable response to this application would significantly facilitate this transition. My long-term goal is to identify the genetic events associated with the development of leukemia in children, and the ability to perform the proposed studies is one step towards this vital goal.